[BREAKING] feat: make resolver preset follow Metro defaults closely

.changeset/kind-scissors-kick.md

@@ -0,0 +1,15 @@
+---
+"@callstack/repack": major
+---
+
+BREAKING CHANGE:
+
+`getResolveOptions` is now way more compatible with `metro-resolver` and `@react-native/metro-config`
+
+1. `getResolveOptions` now accepts a second optional parameter called options with the following properties:
+   - `enablePackageExports` - defaults to `false`
+   - `preferNativePlatform` - defaults to `true`
+2. Order of extensions was changed to match the order from `@react-native/metro-config`.
+3. Resolution via Package Exports (`exports` field in package.json) is now optional and disabled by default.
+   It can now be enabled via `getResolveOptions` options parameter. This change was introduced to match `metro` defaults.
+4. Default `conditionNames` are now: `['require', 'import', 'react-native']` and match `@react-native/metro-config` defaults.

metro-compat-test/jest.setup.js

@@ -9,24 +9,39 @@ const testsToSkip = {
     '[nonstrict] should fall back to "main" field resolution when "exports" is an invalid subpath',
     '[nonstrict] should fall back to "browser" spec resolution and log inaccessible import warning',
     '[nonstrict] should fall back and log warning for an invalid "exports" target value',
-    '[nonstrict] should fall back to "browser" spec resolution and log inaccessible import warning',
-    '[nonstrict] should fall back to "browser" spec resolution and log inaccessible import warning',
     // Assets are handled differently in webpack
     'should resolve assets using "exports" field and calling `resolveAsset`',
     // Resolving fails as expected but error messages are different
     'should use most specific pattern base',
     'should throw FailedToResolvePathError when no conditions are matched',
+    // Root shorthand - pending fix in metro
+    'should expand array of strings as subpath mapping (root shorthand)',
+    // Restricted imports - pending fix in metro
+    'should resolve subpath patterns in "exports" matching import specifier',
+  ]),
+};
+
+const testsToSkipOnce = {
+  describe: new Set(),
+  test: new Set([
+    // sourceExts are expanded, platform-specific extensions are not
+    'without expanding `sourceExts`',
+    'without expanding platform-specific extensions',
   ]),
 };
 
 // alias it to test
 Object.defineProperty(testsToSkip, 'it', testsToSkip.test);
+Object.defineProperty(testsToSkipOnce, 'it', testsToSkipOnce.test);
 
 // trap call & check if test should be skipped
 const handler = {
   apply(target, _, args) {
     if (testsToSkip[target.name].has(args[0])) {
       return target.skip(...args);
+    } else if (testsToSkipOnce[target.name].has(args[0])) {
+      testsToSkipOnce[target.name].delete(args[0]);
+      return target.skip(...args);
     } else return target(...args);
   },
 };

metro-compat-test/resolver/resolve.ts

@@ -101,9 +101,12 @@ function transformContext(
     } as InputFileMap,
     options: {
       // repack uses whole separate config per platform
-      conditionNames: platform
-        ? context.unstable_conditionsByPlatform[platform]
-        : context.unstable_conditionNames,
+      conditionNames: Array.from(
+        new Set([
+          ...context.unstable_conditionNames,
+          ...(context.unstable_conditionsByPlatform[platform!] ?? []),
+        ])
+      ),
       fallback: context.extraNodeModules
         ? { ...context.extraNodeModules }
         : undefined,

package.json

@@ -5,7 +5,7 @@
     "build": "turbo run build",
     "lint": "turbo run lint --filter=!metro-compat-test",
     "typecheck": "turbo run typecheck --filter=!metro-compat-test",
-    "test": "turbo run test --filter=!metro-compat-test",
+    "test": "turbo run test",
     "release": "pnpm build && pnpm lint && pnpm test && pnpm changeset publish",
     "website:start": "turbo run docs && pnpm --filter website run start",
     "website:build": "turbo run docs && pnpm --filter website run export",

packages/repack/src/webpack/utils/getResolveOptions.ts

@@ -1,14 +1,32 @@
 /**
- * Get Webpack's resolve options to properly resolve JavaScript files
- * that contain `<platform>` or `native` (eg `file.ios.js`) suffixes as well as `react-native` field
- * in dependencies' `package.json`.
+ * {@link getResolveOptions} additional options.
+ */
+export interface ResolveOptions {
+  /**
+   * Whether to enable Package Exports support. Defaults to `false`.
+   */
+  enablePackageExports?: boolean;
+  /**
+   * Whether to prefer native platform over generic platform. Defaults to `true`
+   */
+  preferNativePlatform?: boolean;
+}
+
+/**
+ * Get Webpack's resolve options to properly resolve JavaScript files:
+ * - resolve platform extensions (e.g. `file.ios.js`)
+ * - resolve native extensions (e.g. `file.native.js`)
+ * - optionally use package exports (`exports` field in `package.json`) instead of
+ *   main fields (e.g. `main` or `browser` or `react-native`)
  *
  * @param platform Target application platform.
+ * @param options Additional options that can modify resolution behaviour.
  * @returns Webpack's resolve options.
  *
  * @category Webpack util
  *
  * @example Usage in Webpack config:
+ *
  * ```ts
  * import * as Repack from '@callstack/repack';
  *
@@ -17,35 +35,74 @@
  *
  *   return {
  *     resolve: {
- *       ...Repack.getResolveOptions(platform),
+ *       ...Repack.getResolveOptions(platform, {
+ *         enablePackageExports: false,
+ *         preferNativePlatform: true
+ *       }),
  *     },
  *   };
  * };
  * ```
  */
-export function getResolveOptions(platform: string) {
+
+export function getResolveOptions(platform: string, options?: ResolveOptions) {
+  const preferNativePlatform = options?.preferNativePlatform ?? true;
+  const enablePackageExports = options?.enablePackageExports ?? false;
+
+  let extensions = ['.js', '.jsx', '.json', '.ts', '.tsx'];
+
+  let conditionNames: string[];
+  let exportsFields: string[];
+
+  if (enablePackageExports) {
+    /**
+     * Match what React Native uses in @react-native/metro-config.
+     * Order of conditionNames doesn't matter.
+     * Order inside of target package.json's `exports` field matters.
+     */
+    conditionNames = ['require', 'import', 'react-native'];
+    exportsFields = ['exports'];
+  } else {
+    conditionNames = [];
+    exportsFields = [];
+    extensions = extensions.flatMap((ext) => {
+      const platformExt = `.${platform}${ext}`;
+      const nativeExt = `.native${ext}`;
+
+      if (preferNativePlatform) {
+        return [platformExt, nativeExt, ext];
+      } else {
+        return [platformExt, ext];
+      }
+    });
+  }
+
+  /**
+   * Match what React Native uses in @react-native/metro-config.
+   * First entry takes precedence.
+   *
+   * Reference: https://github.com/facebook/react-native/blob/main/packages/metro-config/src/index.flow.js
+   */
   return {
     /**
-     * Match what React Native packager supports.
-     * First entry takes precedence.
+     * Reference: Webpack's [configuration.resolve.mainFields](https://webpack.js.org/configuration/resolve/#resolvemainfields)
      */
     mainFields: ['react-native', 'browser', 'main'],
+    /**
+     * Reference: Webpack's [configuration.resolve.aliasFields](https://webpack.js.org/configuration/resolve/#resolvealiasfields)
+     */
     aliasFields: ['react-native', 'browser', 'main'],
-    conditionNames: ['default', 'require'],
-    extensions: [
-      `.${platform}.ts`,
-      `.${platform}.js`,
-      `.${platform}.tsx`,
-      `.${platform}.jsx`,
-      '.native.ts',
-      '.native.js',
-      '.native.tsx',
-      '.native.jsx',
-      '.ts',
-      '.js',
-      '.tsx',
-      '.jsx',
-      '.json',
-    ],
+    /**
+     * Reference: Webpack's [configuration.resolve.conditionNames](https://webpack.js.org/configuration/resolve/#resolveconditionnames)
+     */
+    conditionNames: conditionNames,
+    /**
+     * Reference: Webpack's [configuration.resolve.exportsFields](https://webpack.js.org/configuration/resolve/#resolveexportsfields)
+     */
+    exportsFields: exportsFields,
+    /**
+     * Reference: Webpack's [configuration.resolve.extensions](https://webpack.js.org/configuration/resolve/#resolveextensions)
+     */
+    extensions: extensions,
   };
 }